Network

With the advent of OFDM for WLAN communications, as exemplified by IEEE 802.11a, it has become imperative to have efficient and reliable synchronization algorithms for OFDM WLAN receivers. The main challenges with synchronization deal with the delay spread and frequency offset introduced by the wireless channel. In this paper, research is done into OFDM WLAN synchronization algorithms, and a synchronizer implementation is presented. This synchronizer performs packet detection; frequency offset estimation, and time synchronization.

Designing of Very Large Scale Integrated Circuits (VLSI) operates at Megahertz and Gigahertz satisfying the design constraints for desired applications is a challenging job due to various reasons like transient time effect, high power requirement and consumption etc. Phase Locked Loop (PLL) is an important integrated circuit used in various areas of communications. Frequency synthesizers when used in Frequency Hopping Spread Spectrum (FH-SS) requires strict timing synchronization between transmitting and receiving system for successfully despreading and the power consumption is also high due to high frequency operation. In this contribution a new scheme has been proposed, in which frequency hopping transmitter and receiver has been operated at intermediate frequency and the same hopping rate was obtained as can be achieved by fast hopping spread spectrum operated at high frequency and therefore requires low speed frequency synthesizers and offers many advantages like more user capability, Low cost and simple amplifiers, filters, ADC and DAC converters requirement. The IFH-SS transmitter and receiver based on proposed intermediate frequency hopping spread spectrum has been experimentally verified. The results of experimental investigation have been presented in the paper. The waveforms obtained at various check nodes have also been presented.

India has the highest number of road accident casualties in the world. Out of 0.5 million accidents occurring every year around 0.2 million people lose their precious life. Most of the people die because of lack of proper first aid and immediate back up services. The information about the accident does not reach to ambulance service very soon after occurrence of the accident. To overcome this problem Accident Recovery System is simulated where a sensor is installed in the car which detects an accident and sends a message to the Administrator. Admin can immediately request for backup service and also alert the cars behind the accident location. Various sensors combined together gives us more faster and reliable detection of accidents on highways through autonomous units on the edge of the road (Road Support Units).The sensors in the car tend to detect any accident that has occurred to the car and send a message to the administrator with the help of Road Support Units which helps a car to be connected in the network. The simulation of the model is done with the help of NetLogo.

In a wireless network, one of the major problem is optimization. Optimization problem is finding the best path from all possible paths. This paper proposes a new architecture called Mixed Layer Design to avoid this problem. Even after providing faster transmission of data we are still facing a problem called throughput in wireless network. This problem is due to the interference of wireless signals. In a wireless network, the signal sent by a terminal will be received by all its neighbouring nodes. If a neighbour (except the destinations) is receiving data from some other terminals at the same time, the signals will collide, and the useful signal will be destroyed, which may result in transmission failure. To solve this problem we are proposing Mixed Signals to avoid the collision of signals. We show that intelligently mixing signals and layers increases network throughput and transmission time.

We proposed a new status based clusterhead election algorithms for mobile ad hoc networks which are responsible for stable clusterhead election for a cluster and maintain a stable clustering by predicting staying time for a cluster and selecting an optimal clusterhead. In proposed method if there is two or more than two cluster heads are within the same radio range, initially clusterhead changes will be delayed up to delay timer. After delay timer expire if both the cluster heads are still in the same radio range, then old new clusterhead change its status from 0 to 1 and become as Clustermember within same cluster. In proposed method old clusterhead within the cluster has priority to act as clusterhead compared to other clusterhead which is coming from other cluster.

Identifying the occurrence of congestion in a Mobile Ad-hoc Network (MANET) is a major task. The inbuilt congestion control techniques of existing Transmission Control Protocol (TCP) designed for wired networks do not handle the unique properties of shared wireless multi-hop link. There are several approaches proposed for detecting and overcoming the congestion in the mobile ad-hoc network. In this paper we present a Modified AD-hoc Transmission Control Protocol (M-ADTCP) method where the receiver detects the probable current network status and transmits this information to the sender as feedback. The sender behavior is altered appropriately. The proposed technique is also compatible with standard TCP.

An efficient Communication helpful to a nation in emergency conditions is discussed. TETRA standard which has been defined by the European Telecommunication Standards Institute ETSI is a digital mobile radio system for voice and data communication in ultrahigh frequency (UHF) band. The main function of the system is to provide alternative service to private/professional mobile radio (PMR) types of users because it has disadvantages. TETRA system has a robust and professional mobile communication through cell type system which enables digital data transmission. It overcomes the traditional PMR telephony. It helps users that require their communication system to provide instant transmission, high reliability. It is reliable system suitable for use by different people and availability with a set of services designed to accommodate the daily use of the system as well as provide support in extraordinary conditions.

For providing security,password is important factor. Now a day in any field security is essential.The textual password is the most common password but the textual password has several issues.The new password scheme is introduced in which images are used as a password known as Graphical password.In this paper, a new password scheme is developed which combines recognition based schemes.In this scheme three levels of security is provided.

High speed research in communication trends demands high data rates with reliable transmission system and has thus led to many new emerging modulation techniques. Orthogonal Frequency Division Multiplexing (OFDM) is one of the most promising technologies for high data rate wireless communications due to its robustness, high spectral efficiency, frequency selective fading, and low computational complexity and easy implementation of Very Large Scale Integrated technology (VLSI) now. Because the OFDM system effectively provides numerous parallel narrowband channels, OFDM is considered a key technology in emerging high-data rate systems such as 4G, IEEE 802.16, and IEEE 802.11n. But there is one main disadvantage of OFDM that is the high peak-to-average power ratio (PAPR) of the transmitter’s output signal on different antennas. High Peak to Average Power Ratio (PAPR) for OFDM system is still a demanding area and difficult issue. By now, for reducing PAPR, numerous techniques have been recommended. In this paper the embedded technique which is a combination of Selective level Mapping (SLM), square root and Discrete Cosine Transform (DCT) based PAPR reduction technique has been analyzed and discussed. The results have been verified in terms of various graphs and plots and have been compared with earlier results. The performance comparison of the proposed scheme with conventional technique has also been presented in the paper.

The key challenge faced by cellular and wireless communication is high data rate and high Quality of Service (QOS).To obtain these requirements communication channel needs to be shared in an efficient manner. The only hindrance that prevents the efficient utilisation of communication channels is multipath fading resulting from increased bit error rate of system (BER) at higher signal to noise ratio (SNR) resulting in overall system performance degradation. Various diversity techniques can be used to mitigate the fading effects. The implementation of MIMO technology makes use of multiple antennas both at transmitter as well as receiver thus allowing the transmission of signal through various independent paths, providing the receiver several replicas of the transmitted signal. This increases the probability that accurate information is detected at receiver. In this paper BER vs. SNR is being analyzed for various modulation techniques and the results obtained are compared with each other. The proposed technique makes use of minimum mean square error ratio (MMSE) to provide satisfactory bit error rate (BER) performance as compared to earlier results of Maximum Ratio combining (MRC)